Dutch Elm Disease

Overview

Dutch Elm Disease (DED) is caused by a fungus that affects Elm trees. The American elm is the most susceptible to this disease, with cedar elm being only moderately susceptible. This disease prevents elm trees from transmitting water from the roots to the crown and eventually causes them to wilt and die. The disease progresses through infected trees very rapidly. A specimen showing early symptoms of the disease will typically die within six to eight weeks.

How the Disease Spreads

The disease spreads in two ways - insect vectors and root grafts. The North American Elm Bark Beetle and the European Elm Bark Beetle are the two insects that typically spread the fungus from tree to tree. The European Beetle, which can travel approximately 2000 feet in their lifetime, is the most prominent in Flower Mound. It is not uncommon for two generations of the beetles to emerge in a typical growing season. In theory, it is possible for the beetles to spread the disease several thousand feet in a growing season. The beetles live and breed under the bark, and they usually target weak or stressed trees. This is why any known diseased trees should be removed and properly disposed of so the beetles don’t have a place to breed. Removal of non-infected, yet stressed trees, is also recommended.

The second way the disease spreads is through root grafts. Roots of trees in close proximity tend to touch and overlap. These roots commonly graft together and share nutrients and water. The grafts can also allow the fungus to move from one tree into another. In cases where several elm trees are located in close proximity, the disease will continue spreading until all of the trees are infected. If one tree is not showing signs of the disease, it is possible to save that tree by severing the root grafts and removing the infected trees; although, this is challenging and should be done quickly after the infected trees are identified.

Contact Us

At this time, it is important that the infected trees are identified and removed to reduce the spread of the beetles. Very little research has been conducted regarding Dutch elm disease in Texas and little is known about how the disease will progress through the state. Early observations indicate that the disease is not slowing down, and is causing damage on both public and private land. For more information, please contact the Town of Flower Mound’s Environmental Resources division at 972.874.6352.